In view of energy saving, lowering motive power in fluid apparatuses and fluid apparatus systems is becoming more and more important. Alleviating vibration and noise ascribable to the fluid apparatuses and the fluid apparatus systems is also very important in view of securing safety and improving work environments in plants.
The inventors studied a phenomenon that plasmatizing part of a fluid makes it possible to control a flow. As a result, the inventors invented an air current generating apparatus generating an air current by the action of plasma and confirmed its effect.
This air current generating apparatus is capable of generating a very thin laminar flow on a flat plate while appropriately controlling the flow. As a result, it is possible to realize such a control of the air current as to vary velocity distribution on a boundary layer of the flow, forcibly change the flow from a laminar flow to a turbulent flow, and generate/eliminate a vortex. This air current generating apparatus is usable as an innovative element technique of various kinds of industrial apparatuses.
A conventional air current generating apparatus generally has the following structure. Specifically, on a first dielectric (insulating plate), a first electrode (counter electrode) in a strip shape is disposed via an adhesive. On the first electrode, a second dielectric (insulating plate) is disposed via an adhesive. On the second dielectric, a second electrode (discharge electrode) having the same shape as that of the first electrode (counter electrode) and having long sides parallel to long sides of the first electrode (counter electrode) is disposed via an adhesive.
A voltage of, for example, about 1 to 10 kV is applied between the discharge electrode and the counter electrode of the air current generating apparatus. Accordingly, air near the second dielectric between these electrodes is ionized and then an air current flowing from the discharge electrode toward the counter electrode is generated along a surface of the second insulating plate.
However, such a conventional air current generating apparatus has the following problems.
Firstly, in the conventional air current generating apparatus, when the discharge electrode is a thin plate-shaped electrode, bonded surfaces of the discharge electrode and the dielectric are likely to peel off from each other as time passes.
The peeling of the discharge electrode may possibly cause the ignition of a discharge in a gap between the peeled portions, resulting in a power loss, or may possibly impair uniformity of an induced air current due to the occurrence of an accidental induced air current, resulting in deterioration in air current control efficiency.
Further, as for the counter electrode, bonded surfaces of the counter electrode and the dielectric are likely to peel off from each other as time passes. This, as a result, may possibly cause a power loss due to the ignition of a discharge in a gap between the peeled portions, or deteriorate dielectric strength of the dielectric due to heat generation, leading to dielectric breakdown.
Secondly, in the air current generating apparatus, in order to form a desired high space-field intensity on a counter electrode-side edge portion of the discharge electrode, thickness uniformity and shape precision are required of the discharge electrode, and high flatness is also required of the surface of the dielectric on which the air current flows. However, the conventional air current generating apparatus is manufactured by a stacking method using an adhesive. This makes it difficult to ensure the precision in the thickness and shape of the electrode and the flatness of the surface of the dielectric.
Thirdly, in the conventional air current generating apparatus, an accidental discharge in a reverse direction is likely to be ignited on an edge portion, of the discharge electrode, on a side distant from the counter electrode. This may possibly cause the generation of an air current from this edge portion in the reverse direction and may possibly impair uniformity of an induced air current, resulting in deterioration in air current control efficiency.
Fourthly, in the conventional air current generating apparatus, an induced air current is obtained at a predetermined velocity in a direction along the surface of the dielectric. However, in the conventional air current generating apparatus, it is difficult for the velocity of the induced air current to have distribution along a longitudinal direction of the discharge electrode and for an induced air current to be generated in a direction perpendicular to the surface of the dielectric.
Fifthly, in the conventional air current generating apparatus, there sometimes occur concavity/convexity and disturbance of an electric field near a portion, of the discharge electrode or the counter electrode, connected to a high-voltage cable. This is likely to deteriorate air current control efficiency due to the disturbance of the induced air current.
Sixthly, in order to complicatedly control the air current on an object surface by the conventional air current generating apparatus, it is necessary to arrange a plurality of the air current generating apparatuses on the object surface and control them simultaneously. This requires a power source, a switching circuit, and a control device which are complicated and large-scaled. There is also a concern that air current control efficiency may deteriorate due to the interference of electric fields formed by a plurality of electrodes.
Seventhly, the conventional air current generating apparatus also has problems from a practical viewpoint, such as high manufacturing cost of the electrodes, inferior durability, and easiness of the occurrence of electric noise.